Luminous intensity (brightness) of an illumination light source such as a light emitting diode (LED) is known to change generally depending on temperature. Therefore, for example, if an image at a time of being irradiated with light emitted from an illumination light source is photographed, the brightness of the image changes depending on temperature. Accordingly, a technology is disclosed including measuring temperature of an illumination light source, and checking the measured temperature against temperature characteristics of the illumination light source, thereby driving and controlling the illumination light source such that the luminous intensity of the illumination light source becomes optimum (for example, see Patent Literature 1).